The Boswell Sisters were a sensation in the 1930s. They take center stage in the article Pitch Perfect: A History Of Vocal Groups. They used the term "Rock and Roll" in a song in 1934, before anyone had an idea that those words might catch on.
As jazz took hold in the 20s, there was a dip in the popularity of vocal groups, but waiting in the wings were The Boswell Sisters, a group who changed the face of modern music in the 30s after they emerged from the vaudeville houses of New Orleans. They were true innovators and can easily claim to be one of the all-time greatest jazz vocal groups.Then again, there are a lot of vocal groups you can read about in the article at udiscovermusic. (via Everlasting Blort)
The sisters were talented musicians. Martha played piano; Vet played violin, banjo and guitar; and Connee (who had been left paralysed from the waist down by a childhood accident, and always performed sitting down) played cello, saxophone and guitar. The turning point in their career came when a radio station gave them a daily singing programme.